Actuating mechanism for loud speakers



April 1929. c. L. FARRAND ET AL 1,707,222

ACTUATING MECHANISM FOR LOUD SPEAKERS Filed Nov/5, 1926 2 Sheets-Sheet 1 ATTORN EYS April 1929- c. L. FARRAND ET AL 1,707,222

ACTUATING MECHANISM FOR LOUD SPEAKERS Filed Nov. 5, 1926 2 Sheets-Sheet 2 JAYLENTOR flu, 7374 ATTORN EY5 Patented Apr. 2, i929.

oni'rs CLAIR L. FARRAND, QF FOREST HILLS, NEW YORK, AND ERNEST BOSS, 033 EAST ORANGE, NEW JERSEY; SAID ROSS ASfiIGNOR TO FAB-RAND MFG. CO. INC, OF LONG ISLAND CITY, NEW YORK, A QOREOEATION 0F JERSEY.

AGTUATING MECHANISM FQR LOUD-SPEAKERS.

Application filed. November 5, 1926. Serial No. 148,349.

This invention relates to loud speakers and more particularly tosan improved electromagnetic actuating device or so-called driveffor the diaphragm.

T he main object of the'invention is to provide simple and effective means for transmitting vibrations from an armature to the diaphragm when the armature vibrates in a plane which is substantially parallel to the general plane of the diaphragm.

l'inotl'ier object is to make it possible to position the magnet of the driver in a plane substantially parallel with the general plane of the diaphragm even when the armature vibrates in the general plane the magnet.

In that type of actuating device in which the armature vibrates in the general plane of the magnet the connection of the armature to the diaphragm may be etl'ecteo in a simple manner if the magnet is positioned in a plane substantially at right angles to the general plane of the diaphragm because then the armature vibrates toward and away from the diaphragm. However this arrangement 7 of the magnet is objectionable because the magnetoccupies more room in the axial direction of the speaker and it is more difficult to mount the magnet in this position. In some loud speakers the pole pieces of the magnet are overlapped in such a way that the armature vibrates toward and away from the diaphragm in a plane which is at right angles to the general plane of the diaphragm and this makes it possible to position the magnet in a plane which is substantially parallel to the general plane of the diaphragm and to employ relatively simple connections from the armature to the diaphragm. 'However, we prefer not to overlap the pole pieces, but to preserve their simplicity, and yet we prefer to mount the magnet in a plane substantially parallel to the general plane of the diaphragm, so we employ special transmission connections from the armature to the diaphragm so arranged that the vibrations of:

the armature, which take place in a plane parallel to the general plane of the diaphragm are changed in their direction and imparted to the diaphragm in a direction which is at right angles to the general plane of. the diaphragm.

The accompanying drawings illustrate an electromagnetic actuating device constructed,

in accordance with the invention and also show the actuating device applied to a loud speaker.

In the drawings:

Fig. 1 is a top plan View of the actuating device;

Fig. 2 is a side elevation thereof;

Fig. 8 is a front elevation of-the actuating device; i

Fig. at is a detail perspective view showing the connections between the armature and the diaphragm; and

Fig. 5 is a broken side elevation of a loud speaker provided with the improved actuating device. v

Referring first to Figs. 1 to 4 inclusive the driver or electromagnetic actuating device comprises a permanent magnet 1 to one pole of which is fastened a pole piece 2 and to the other pole of which is fastened a pole piece The pole pieces 2 and 3 extend toward each other as shown in Fig. 3 and the adjacent ends of the pole pieces are bifurcated so as to provide a central rectangular opening 4 and so as to form poles :2 and 2 on the pole piece 2 and poles 3 and 8 on the pole piece 3. The pole pieces 2 and 3 are so positioned as to leave an air gap between the poles 2 and 3 and a similar gap between poles 2 and 3 in which an armature 5 vibrates. An aluminum casting 6 is secur d to the pole pieces 2 and 3 and this casting serves as a housing for the speech coils and also serves as a mechanical support for the armature and for the mechanical connections from the armature to the diaphragm. This casting is preferably made in two parts, one of the parts shown at 6 being attached to the outer faces of the two pole pieces 2 and 3 and the other part 6 being attached to the inner faces of the two pole pieces 52 and 3. The parts of the aluminum casting 6 may be attached to the pole pieces in any suitable way as by means of screws 7 which pass through holes in the pole pieces and are threaded into the rear section 6" of the aluminum casting in such away as to clamp the two halves of the aluminum casting to each other and to the pole pieces. The aluminum casting 6 forms a support for the two ends of a flat spring 8 to the center portion of which the armature'5 is soldered as shown in Fig. &. It Will be noted from this figure fit that the flat spring and the armature intersect each other, and the plane of the spring is substantially at right angles to the plane of the armature. One end of the armature 5 lies between the poles 2 and 3 and the other end of the armature lies between the poles 2" and 3 and the spring 8 yieldingly holds the armature in its central position between the two pairs of poles. Instead of attaching the spring 8 at its ends to stationary portions of the aluminum castings 6, each end of the spring is preferably secured by means of a screw 9 to a semi-cylindrical block 10 capable of being turned in a cylindrical seat 11 when the adjusting screws 12 and 13 are manipulated. It will be noted that the screws 1-2 and 13 are threaded into the aluminum casting 6 and the heads engage over the edge portions of the semi-cylindrical block 10 so that when one of the screws is loosened and the other tightened, the semi-cylindrical. block 10 is turned in its seat. In this my the plane of the spring 8 may be tilted slightly in. order to adjust the position of the armature extremities between the poles. It will be understood that there is one of these semi-cylindrical blocks 10 at each end of the spring 8 but only one of them shows in the drawing. I

A three part lever 12 12 --12 is connected at one end by means of a screw 13 to an upstanding projection 14 at one corner of the aluminum casting 6, and is secured at its other end by means of a screw 14 to an upstanding projection 15 at the opposite corner of the aluminum casting 6. As best shown in Fig. 4 the three part lever 12 12 12 is preferably in the form of a channel shaped strip of sheet metal the side flanges 16 of which are cut away at the points marked 17 and 18 so that the lever may be bent to the shape shown in Figs. 1 and 4 and so as to provide a flexible hinge portion 19 located between the portion 12 and the portion 12 and the hinge portion 20 located between the portion 12 and the portion 12 The extreme end portion of the part 12 where it is his tened to the projection 14 is not flanged and likewise the extreme end portion of the part 12 where it is fastened to the projection 15 is not flanged. A pin or red 21 is soldered at one end to one end of the armature 5 and at its other end is soldered to the lever 12 12 --12 approximately at the hinge portion 19. A red or pin 22 is soldered to the lever portion 12 preferably midway between the ends of the latterand this rod extends to and is connected with the apex of the conical diaphragm, as will be hereinafter described.

The aluminum casting 6 houses a pair of speech coils 23 and 24. Each of these coils encircles an end portion ofthe armature 5. The coils are held stationary in the aluminum casting 6 and the armature 5 is free to Vibrate Within the coils. The rectangular opening 4 formed by the bifurcation of the pole pieces 2 and 3 accommodates the coils 23 and 24 and at the same time forms projecting poles which extend over the faces of the coils toward the armature as clearly shown in Fig. 3.

lVhen the coils 23 and 24 are energized by a varying current, the armature 5 is vibrated in accordance with the variations in the current passing through the coils in the'well known manner. The vibrations of the armature 5 vibrates the rod 21 longitudinally, the vibration of the latter being imparted to the lever portion 12 The flexibility of the lever portion 12 immediately adjacent to the projection; 14, which flexibility exists approximately at the place marked causes this part of the lever portion'12 to act as a fulcrum or hinge so that the lever portion 12 vibrates about the part 25 as a hinge, The motion of the lever portion 12 at the hinge 19 is transmitted through the lever portion 12 to the lever portion 12 The lever portion 12 vibrates about the part 26 as a hinge due to its flexibility at this point. The amplitude of vibration of the lever portion 12 at the hinge 20 is the same as the amplitude of vibration of the lever portion 12 at the hinge 19, because the connecting lever portion 12 makes the same angle with the lever portion 12 that it doeswith the lever portion 12 The rod is vibrated longitudinally by the lever portion 12 Thus the vibrations of the armature which takes place in the direction of the rod 21 are changed in direction so that they are ultimately transmitted to the diaphragm in the direction of the rod 22 which, it will be noted, is disposed at right angles to the rod 21.

It will now be noted that the lever 12 12 -12 acts the same way as if it comprised two se )arate end levers pivoted to the aleminum casting 6 and arranged at right anp' 2:" to each other, and an intermediate connet lever pivoted to the adjacent ends of the n mentioned levers. However, the construction shown and described eliminates the necessity of providing separate levers with pivotal connections between them, been. .se the same result is obtained by using one strip of metal stamped and shaped as shown in the drawings.

Fig. 5 shows the actuating mechanism or driver above described applied to a loud speaker of the double cone type, but it may also be used. for loud speakers having diaphragms of other types. In Fig. 5 the diaphragm structure of the loudspeaker comprises a cone 25 made of paper and a. cone frustum 26 which may also be made of paper.

The cone 25 and cone trust-um 26 are cemented together at their meeting ed ges and an ornamental cord 27 surrounds the diaphragm structure to conceal the joint between the cone and the cone trustum. The cone frustum 26 has its edge portion clamped in a ring structure 28 the details of which have no bearing on the present invention. The ring'structure 28 is supported by a pair of rods 29 and 30 which pass downwardly through the interior oi? the cone structure to a supporting base 31, an opening being pro-- vided in the lowermost portion of the diaphragm structure to permit the passage therethrough of the rods. The rods 29 and 30 are secured at their lower ends to tile base 31. in the particular loud speaker shown in the drawings the actuating device is also mounted on the rods 29 and 30. One leg elf the magnet at its upper end is clamped to the rod 29 by means of a bolt 32 and the other leg of the magnet at its upper end is clamped to the rod 30 by means of a similar bolt These bolts and 33 may also serve to clamp the pole pieces 2 111d 3 to the poles of the magnet. The lower end of the magnet may be clamped against rods 29 and 30 by means of a bridge piece 34 and a bolt The belt 35 is located between the rods 29 and 30 and clears the mag netitselt, but it passes through a flange 36 on the ring structure 28 and the effect is to pull the magnet against the rods 29 and 30 be cause these rods are also fastened to the flange 36. It will. be seen from Fig. 5 that the rod 22 is connected at its end to the apex out the cone 25 by means of a colletand clutch device 37 the details of which term no part of the present invention. tions or" the rod 22 vibrate the conical diaphra gin in the well known manner.

It will now be seen that the magnet of the actuating device may be mounted in a plane which is substantially parallel with the general plane of the diaphragn'i. hen positioned in this plane the armature vibrates in a direction which is at right angles to the direction in which it is necessary to impart the vibrations to the diaphragm. However, the three part lever l2 l2 12 changes the direction of the vibrations of the armature and transmits them to the diaphragm inthe proper direction. The means employed for doing this is simple in construction and inexpensive to numutacture as t naybe a eless, it

simple metal stamping. Ncvert 1 1S highly eliicient in accomplishing t io desired The longitudinal vibra-' tions of the armature into vibrations which talreplace substantially at right angles to the general plane ofthe diaphragm.

2. A loud speaker comprising a diaphragm, a magnet mounted in a plane substantially parallel with the general plane of the diaphragm, an armature vibrating in a plane substantially parallel with a plane oi the magnet and means for transn'iitting the vibrations from the armature to the diaphragm, said means comprising a strip of sheet metal tulcrumed at its ends and having three sections one of which is vibrated by the arinature'and another of which is connected with the diaphragm, said strip of sheet metal being arranged to convert the vibrations of the armature into vibrations which are substantially at right angles to the general plane of the diaphragm.

A loud speaker comprising a diaphra m, an electromagnetic actuating mechan in therefor compi sing a magnet, a vibratory armature, a three part lever having end portions and an intermediate portion the end portions being arranged at right angles to each other and fulcrumed at their outer ends and the intermediate port-ion being hingedly connected to the adjacent extremities of the end portions of the lever, a connection from the a mature to one 01 the can portions 01' the lever and a connection from the other en portion of the lever to the diaphragm.

-;l-. A loud speaker in accordance with claim 3 in which the three part lever comprises a sheet metal stamping.

A loudspeaker in accordance with claim 3 in which the three part lever comprises a. channel shaped sheet metal strip the s flanges of which are cut away to turnish hinging flexibility between the lever port and the extreme end portions of the lever ing flat tor the purpose described.

6. A loud speaker in accordance with claim 3 in which the three part lever comprises a continuous metal strip, the lever portions themselves between the hinges having side flanges to insure rigidity.

7. A loud speaker comprising a diaphragm, a magnet disposed in a plane substantially parallel with the general plane of the diaphragm, an armature, a rod connected to the arn'iature and arranged in a plane substantially parallel withv the general plane of the diaphragm, second rod connected to the diaphragm and disposed substantially at right angles to the first named rod, and connections for imparting vibrations from the first named rod to the second named rod, said connections comprising a three-part lever having end portions and an intermediate portion, one end portion being fulcrumed at its outer end and arranged at right angles to said first named rod on the armature and connected with said rod, the other end portion being fulcrumed at its outer end and arranged at right angles liellllG and arranged in a pl:

to said second rod and being connected there-- with, and. the intermediate portion of the lever being hingedly connected to the adjacent extremities of the end portions of the lever.

8. A lon d speaker comprising a diaphragm. electromagnetie actuating mechanism for the diaphrz'tgm having an armature vibrating in a plane parallel with the general plane of the diaphragm, a rod connected to the 1e snbstantn parallel with the general plane of the diaphragm, a second rod connected to the diaphragm and disposed substantially at right angles to the first named rot. and conr tions for innaarting vibrations from the first named rod to the SCCOIi'fl named rod, said connections comprising a three-part lever having end portions and an intermediate portion, one end portion. being l'nlernined at its outer end and arranged at right angles to said flrstnamed rod on the rmatnre and connected with said rod. the other end portionbeing fulcrnmed at its outer end and arranged at right angles to said second rod and being connectedtherewith and the intermediate portion of the lever being hingedly connected to the adjacent extremities of the end portions of the lever.

9. An eleetro-magnet having a vibratable armature, in combination with a motion transmitting member in the form of loop anchored at its ends and connected between its ends with said armature, said loop having a flexible portion and a rigid portion.

10. An eleetro-magnet having a vibratable armature, in combination with a motion transmitting member in the form of a loop anchored at its ends and connected between its ends with said armature, said loop having a flexible portion and rigid portions between which the flexible portion is located.

11.. An electro-magnet having a vibratable armature, in combination with a motion transmitting member in the form of a loop and connected between its ends with said armature, said loop l'laving two flexible portions and a rigid portion between said flexible portions.

12. An electro-magnet having a vibratable armature, in combination with a motion transmitting member in the form of a loop and connected between its ends with said armature, said loop having three rigid portions and a flexible portion between the intermediate rigid portion and each remaining rigid portion.

13. An eleetro-magnet having a vibratable armature, in combination with a motion transmitting member in the form of a loop and connected between its ends with said ar y mature, said loop having three rigid portions and a flexible portion between the intermediate rigid portion and each remaining rigid portion and other flexible portionsat its ends.

14. An electro-magnet having a vibratable armature, in combination with a motion transmitting member in the form of a loop anchored at its ends and connected between 7 tures.

CLAIR- L. FARRAND ERNEST ROSS. 

